Vapor generator



20, w47. L, BOLAND 2,420,647

VAPOR GENERATOR 1NVENTOR. Edward L Boland ATTORNEY May 20, 1947- E. 1BOLAND k 2,420,647 VAPOR GENERATOR Filed July s. 1942 2 sheetslsheet. 2

ATTORNEY Patente'd May 20, 1947 UNITED STATES PATENT OFFICE 2,420,647VAPORLGENERATOR Edward L. Boland, East Orange, N. J., assignor to TheBabcock & Wilcox Company, Jersey City, N. J., a corporation of NewJersey Application July 8, 1942, Serial No. 450,109

3 Claims.

The present invention relates to marine power plant installations of thegeared turbine type having a separate astern turbine or turbine stagefor stopping and backing, and more particularly to installations of thistype incorporating a steam reheat cycle in which the steam for theastern turbine orturbine stage does not pass through the reheater, andin which under stand-by conditions and in port the installation must beoperated to supply saturated o-r superheated steam for the auxiliarieswith no flow through the reheater.

The general object of my invention is the provision of a steamgenerating unit which is particularly adapted for use in a marine powerplant installation of the character described. A further and morespecific object is the provision of a steam generating unit having highthermal efflciency, an arrangement and proportioning of the superheatersurface therein providing a steam superheat temperature within safeoperating limits at all times, a capacity for maintaining constantsuperheat and reheat steam temperatures, and adequate protection of thereheater during periods ci low or no steam ow therethrough` The variousfeatures oi novelty which characterize my invention are pointed out withparticularity in the claims annexed to and forming a part of thisspeciiication. For a better understanding of the invention, itsoperating advantages and specic objects attained by its use, referenceshould be had to the accompanying drawings and descriptive matter inwhich I have illustrated and described a preferred embodiment of myinvention.

Of the drawings:

Fig. l is a simpliiied diagram of the piping lay-out between the steamgenerating unit and associated turbines;

Fig. 2 is a sectional elevation of a steam generating unit constructedin accordance with my invention; and

Fig. 3 is a horizontal section taken on the line 3 3 of Fig.v 2.

In one marine power plant installation of the reheat cycle type forwhich rny improved steam generating unit is particularly adapted, steamis supplied to a high pressure turbine at a pressure of approximately1250 p. s. i. and temperature of '750 F. The steam is then expandedthrough the high pressure turbine and delivered to a reheater at aninlet pressure of approximately 230 p. s. i. and then reheated at thisreduced pressure to its initial temperature of '750 F. The reheatedsteam then passes serially through the intermediate and low pressureturbines of the installation. In the use of a reheat cycle in a marineinstallation certain operating conditions peculiar to marine servicemust be given special consideration. With a separate astern turbine orturbi -e stage for stopping and backing the vessel, the steam i or theastern turbine is not passed through the reheater. Under such conditionsa greater amount 0f fuel is required to be burned in the main boilerfurnace for iull speed astern than for normal speed ahead. The resultingincreased volume of hot gases' contacting the superheater under suchconditions is likely to cause heating of the superheater tubes above thedesired superheat temperature and possibly beyond a safeoperatingtemperature. Furthermore, the generating unit must be operated understand-by conditions and in port to supply saturated or superheated steamor the auxiliaries with no new through the reheater.

The use of a separate steam heated reheater in an installation of thecharacter described. has been proposed. Steam reheat however, is lesseicient than combustion gas reheat because the reheat temperature usinglive steam as the heating medium is limited to the saturationtemperature corresponding to the boiler steam pressure. Due

to this inherent limitation, the full possibilities y of the reheatcycle cannot be utilized, whereas with combustion gas reheat the steamcan be reheated to any temperature the materials used will stand,permitting, for example, reheating to the original superheated steamtemperature.

The steam generating unit illustrated in Figs. 2 and 3 is in general ofthe double furnace single uptake type illustrated in the copendingapplication of Edward J. Rooney, Ser. No. 228,734,

tiled Sept. 7, 1938, now U. S. Patent 2,332,534, The unit comprises anupper horizontally elongated steam and water drum lll, a laterallyoffset bottom supported lower water drum i i connected to the drum IIJby a vertically inclined main bank of steam generating tubes l2. Asecond bottomsupported lower water drum I3 is positioned below the drumand connected thereto by laterally spaced groups of Water tubes lil. Thespace within the setting between the tube groups l2 and lll forms themain furnace chamber l5, in

l the double front of which a pair oi liquid fuel burners I5 arehorizontally arranged. The portion of the setting at the opposite sideof the tube groups i4 serves as an auxiliary furnace chamber Il which isindependently fired by liquid fuel burners I8. The outer side wall ofthe furnace chamber I1 is coole-d by a row of refractory covered tubesI9 having their lower ends connected to a side wall header Z and theirupper porti-ons sloping along the furnace roof and connected to the drumIS.

A common heating gas outlet flue 25 for the furnaces I5 and I'I isarranged at the outer side of and above the main tube bank l2. A tubulareconomizer 26 and air heater 2l are located therein for increasing thethermal eihciency of the unit. The setting is of the double walled type,permitting a flow of combustion air therethrough to the double front ofthe unit and the air registers of' the fuel burners I6 and I3. Downcomertubes 28 are arranged within the rear double wall of the setting forsupplying water from the drum I5 to the drums I I and I3 and header 25.

In accordance with my invention the steam superheating surface of theunit is divided into two spaced sections, a primary superheater sectionreceiving heat by convection from the auxiliary furnace only, and asecondary superheater section receiving heat by convection from both themain and auxiliary furnaces. The primary section is formed by a group ofhorizontally looped nested tubes 33 extending between a pair of verticalheaders Sil and 35 at the front end of the unit, the header 34 beingsubdivided to provide a two-pass steam ow through the primary sectionand steam inlet and outlet connections thereto. The primary section ispositioned in the upper part of the vertically elongated space 35between the groups of water tubes I 4 and supported by plates carried bylarge diameter water tubes SI extending between the drums It) and I3.The secondary superheater section is arranged within a space 38 withinthe tube bank I2 and consists of an inclined row of looped tubes 4!extending between a pair of inclined headers lll and 42 extendingparallel to the tubes I2 and subdivided to provide a three-pass steamflow therethrough. The tubes do are similarly supported by largediameter tubes 44 extending between the drums Ill and II. The headers34, 35, (1I and l2 are positioned in the front double wall of thesetting so that access thereto is not blocked by the downcomer tubes 28.The upper end of the header Sil is connected to the drum IE). The headeril is connected at its upper end to the steam outlet of the header 34,while the lower end of the header 42 is connected to the steam lineleading to the high pressure turbine. Where saturated steam is requiredfor the auxiliaries, a branch connection is led from the secondarysuperheater outlet to a coil within the water space of the drum Ie fordesuperheating steam for the auxiliaries, as indicated in Fig. 1.

A steam reheater is also incorporated in the unit and arranged in alocation permitting eilicient operation of the unit whenever superheatedsteam with no reheating is desired while affording ample protection tothe reheater during such periods, and in addition providing an accuratecontrol of the reheated steam outlet temperature when the reheater is inoperation. The steam reheater is formed by horizontally arranged nestedrows of single looped tubes 50 occupying the remaining portion of thespace 3S between the tube groups I 4. The tubes 55 have their endsconnected to vertical headers 52 and 53, which may be separate or, asshown, integral with the superposed headers 34 and 35 respectively. Theheader 52 is subdivided to provide a two-pass steam flow through thereheater with a steam inlet connection at the upper end of the headerand reheated steam outlet at the lower end. The

tubes are supported from the water tubes 31 in the same manner as theprimary superheater tubes 33. The row of water tubes I4 adjoining themain furnace I5 have their lower portions provided with metallic studsand refractory to dene a partition or baffle 55 extending from the drumI3 substantially the full height of the reheater. The partition 55provides an effective protection from flame radiation for the reheaterwhen the main furnace I5 alone is operated. Such protection is essentialduring periods of low or no steam ow through the reheater. The partition55 is also advantageous in tending to confine the flow of heating gasesfrom the auxiliary or reheater furnace I1 to the portion of the mainfurnace I5 substantially above the level of the fue] burners I6 therein,thus avoiding interference with fuel ignition and combustion in the mainfurnace chamber. Short tube bales 56 and 51 at the lower and upper endsof the space 5t at the auxiliary furnace chamber side thereof direct theflow of heating gases from that furnace across the primary superheatersection and reheater.

In operation, both the main and auxiliary furnaces are capable ofgenerating steam and providing superheat. Reheating is provided by theoperation of the auxiliary furnace alone. When reheating is notrequired, such as in startingup or port operation or movements of thevessel astern or during maneuvering, the main furnace l5 alone is used.The reheater section of the unit is normally put in service afterapproximately one-fourth power has been reached and steady operation orincreased power is expected. The reheat temperature is graduallybuilt-up to avoid undue strains in the piping and turbines. The amountof fuel required in the main furnace for full astern operation. isapproximately one and one-half times that required for normal speedahead in the same furnace. The subdivision of the superheating surfaceinto two sections and the location of th'e primary section out of thepath of the gases from the main furnace prevents a total rise in thesuperheated steam temperature under such maximum operation of the mainfurnace alone above a predetermined value, such as 750 F., and therebyprevents the steam temperature to th'e astern turbine stage fromexceedinga safe operating limit. In the full power ahead conditionappreciably less fuel is burned in the main furnace, so that theresulting temperature of the steam heated in the secondary superheatersection alone would be well below '750 F. The controlled operation ofthe auxiliary furnace under such conditions for heating the primarysuperheater section and reheater insures the delivery of superheatedsteam to the high pressure turbine and reheated steam to theintermediate pressure turbine at the desired temperatures.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

I claim:

l. A steam generating unit comprising a setting, an upper steam andwater drum, a laterally oiset lower water drum, an inclined bank ofsteam generating tubes connecting said drums, a second lower water drumbelow said upper drum, a vertical bank of steam generating tubesconnecting said upper drum and second water drum, said tube banksdefining opposite sides of a main furnace chamber therebetween, meansforming an auxiliary furnace chamber at the outer side of said verticaltube bank, means for independently firing said furnace chambers, aheating gas outlet at the outer side of said inclined tube bank forreceiving all of the heating gases from both of said furnace chambersafter flowing over the tubes of said inclined tube bank, a primarysuperheater section arranged in the upper part of said vertical tubebank, a secondary superheater screened from said main furnace chamber bytubes of said inclined tube bank and arranged to be traversed by heatinggases from both' of said furnace chambers, a steam reheater arranged inthe lower part of said vertical tube bank, and means forming a partitionextending between said reheater and main furnace chamber and arranged toshield said reheater from flame radiation from said main furnacechamber.

2. A steam generating unit comprising a setting, an upper steam andwater drum, a laterally offset lower water drum, an inclined bank ofsteam generating tubes connecting said drums, a second lower water drumbelow said upper drum, a vertical bank of steam generating tubesconnecting said upper drum and second water drum, said tube banksdefining opposite sides of a main furnace chamber therebetween, meansforming an auxiliary furnace chamber atl the outer side of said verticaltube bank, means for independently firing said furnace chambers, aheating gas outlet at the outer side of said inclined tube bank forreceiving all of the h'eating gases from both of said furnace chambersafter flowing over the tubes of said inclined tube bank, a primarysuperheater section receiving steam from said upper drum and havinglooped tubes arranged in the upper part of said vertical tube bank, asecondary superheater in series with said primary sectionrand screenedfrom said main furnace chamber by tubes of said inclined tube bank andarranged to be traversed by heating gases from both of said furnacechambers, a steam reheater having looped tubes arranged in the lowerpart of said vertical tube bank, a common tube support for said primarysuperheater and reheater looped tubes, and means forming a partitionextending between said reheater and main furnace chamber and arranged toshield said reheater from flame radiation from said main furnacechamber.

3. A steam generating unit comprising a setting, an upper steam andwater drum, a laterally offset lower water drum, an inclined bank ofsteam generating tubes connecting said drums, a second lower water drumbelow said upper drum, a vertically extending bank of steam generatingtubes connecting said upper drum and second water drum, said tube banksdefining opposite sides of a furnace chamber therebetween, means forminga, second furnace chamber at the outer side of said vertical tube bank,means for independently ring said furnace chambers, a heating gas outletat the outer side of said inclined tube bank for receiving all of theheating gases from both of said furnace chambers after flowing over thetubes of said inclined tube bank, a superh'eater section receiving steamfrom said upper drum and having looped tubes arranged within the upperpart of said vertical tube bank, a separate steam reheater having loopedtubes arranged Within the lower part of said vertical tube bank, acommon tube support for said superheater and reheater looped tubes, andmeans forming a partition positioned between said reheater and rst namedfurnace chamber and arranged to extend from said second lower water drumto substantially the fullheight of said steam reheater so as to shieldsaid reheater tubes from flame radiation from said first named furnacech'amber.

. EDWARD L. BOLAND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS l Number

